Digital cameras are widely used which convert images captured by a solid state imaging device, such as a CCD, into digital image data and store the data in recording media such as an internal memory and a memory card. The solid state imaging device in such digital cameras includes a semiconductor substrate on which light receiving elements (photodiodes) are arranged in a matrix form, a light shielding layer placed on the semiconductor substrate and having openings on each of the light receiving elements, and microlenses located above the light shielding layer. Light rays from an imaging optical system are converged by the microlenses and transmitted through the openings to the light receiving elements.
In these days, the solid state imaging devices are becoming even smaller yet hold more pixels, and the openings are getting smaller in dimension accordingly. As a result, it is becoming difficult to focus light rays toward the light receiving elements strictly by the conventional microlenses. In view of this deficiency, Japanese patent laid-open publication No. 2002-094038 discloses a solid state imaging device with an in-layer lens structure located between the photodiodes and the color filter so as to improve the focusing efficiency.
This solid state imaging device also has a reflective metal film, underneath the in-layer lens structure, to reflect light into the photodiodes.
Even with this structure, however, the focusing efficiency is hardly improved to a considerable extent, and a kind of noise, or so-called smear that appears as white streaks on the photographed image may sometimes be caused. Namely, the incident light that would normally go through the opening of the light shielding film and enter the photodiode is insufficiently focused, and enters the transfer electrode proximate to the photodiode. Such light induces electrical charge in the transfer electrode, which will cause the smear.
Additionally, some kinds of light may even penetrate the reflective metal film located underneath the in-layer lens structure of the above prior art device. Again, in this case, the smear will be caused.